Study Of All-optical Quantization Scheme For All-optical Random Number Generator

Random numbers are widely used in communication and computing, suchas information security, quantum cryptography system and computer simulationsand so on. Random number can be divided into two categories: deterministicpseudorandom number and nondeterministic physical random number. Theformer is generated from a single random seed utilizing deterministic algorithms,though this method can produce high-speed pseudorandom numbers, it isvulnerable when such pseudorandom numbers are used as the keys to encryptionand parallel computation systems. True random numbers are generated fromphysical random phenomena, so true random numbers are of high security fortheir properties of un-predictable, un-reproducible and statistically unbiased.Thus leading true random numbers to wide research and application.True random numbers generated from physical entropy sources is classifiedinto three categories of electronic technique, photoelectronic technique and all-optical technique. Electronic analog-to-digital converting technique has beenrather mature up to now, but the speed of this kind of analog-to-digital convertoris limited by the physical limits of electron migration rate, thus ultimatelylimiting the development of the bandwidth. All-optical analog-to-digitalconverting technique processes signal in optical domain, hence it is able toovercome the limitation of “electronic bottleneck”, leading to its ability to solvethe problems in electronic analog-to-digital conversion. Considering all of above,we propose a random number generator scheme through all-opticalanalog-to-digital conversion. All process in this scheme is dealt in opticaldomain, which can effectively overcome the “electronic bottleneck”, resulting toa large scale of raise in the speed of random number generator.All-optical analog-to-digital conversion including sampling, quantizing andencoding. We mainly make research on all-optical quantization in this article.The major works in this article are as follows:1. By stating the importance of analog-to-digital convertor (ADC) inmodern information processing and communication, as well as the limitation ofelectronic ADC, we illustrate the significance, advantage, background and thestudying history of photonic analog-to-digital converting technique. We alsointroduce and compare several kinds of all-optical quantizing principle andscheme; then declare the research significance of this article.2. In the section chapter, we introduce the construction and properties ofquarter wavelength phase-shifted DFB laser, as well as the optical quantizing principle using this kind of laser. Constructing the theoretical model of quarterwavelength phase-shifted DFB laser according to coupled-wave equations andtransfer matrix method.3. We detailed analyze the static bistability of quarter wavelengthphase-shifted DFB laser in the third chapter. Including the specific influence ofcurrent bias, coupling coefficient, facet reflectivity and chip length to thebistability, and we evaluate the influence through the parameters of highthreshold, width of bistable domain, extinction ratio and slope of the bistability.4. In the forth chapter, we dynamically analyze the function of all-opticalcomparison with the selected parameters obtained through static analyze. Wedemonstrate a result of high resolution of threshold and high extinction ratio,declaring the feasibility of optical quantization with quarter wavelengthphase-shifted DFB laser.5. Summarize the content of this article and propose the future developingprospect.